Preparation of alkadienoic acid esters

ABSTRACT

ESTERS OF ALKADIENOIC ACIDS ARE PREPARED THROUGH THE REACTION OF C4-C12 ALIPHATIC, ACYCLIC, CONJUGATED DIOLEFINS WITH A C1-C20 MONOHYDROXY ALCOHOL AND EITHER GASEOUS CARBON MONOXIDE OR GASES CONTAINING CARBON MONOXIDE IN THE PRESENCE OF A CATALYST SYSTEM INCLUDING ZEROVALENT PALLADIUM. A PREFERRED CATALYST SYSTEM IS COMPRISED OF A ZEROVALENT PALLADIUM MATERIAL AND A PHOSPHINE ACTIVATOR. THE REACTION IS CONDUCTED AT MODERATE TEMPERATURE AND PRESSURE CONDITIONS. THE ALKADIENOIC ACID ESTERS AND THEIR HYDROGENATED DERIVATIVES ARE USEFUL AS SOLVENTS, BRAKE FLUIDS AND PLASTICIZERS.

United States Patent 3,780,074 PREPARATION OF ALKADIENOIC ACID ESTERS Michael G. Romanelli, New York, N.Y., assignor to Esso Research and Engineering Company No Drawing. Continuation-impart of applications Ser. No. 808,672 and Ser. No. 808,673, both Mar. 19, 1969, now Patents Nos. 3,670,029 and 3,670,032 respectively. This application June 3, 1971, Ser. No. 149,774

Int. Cl. C07c 67/00, 69/52 US. Cl. 260-410.9 R 12 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of copending applications: Ser. No. 808,672 filed Mar. 19, 1969, now US. 3,670,029 and Ser. No. 808,673 filed Mar. 19, 1969, now US. 3,670,032.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for the formation of novel alkadienoic acid esters. More particularly the invention relates to a method for securing alkadienoic acid esters through the liquid phase reaction of aliphatic, acyclic, conjugated diolefins with a monohydroxy alcohol and carbon monoxide in the presence of a catalyst based upon zerovalent palladium. The overall reaction involves dimerization of the conjugated diolefin and the addition of both carbon monoxide and an alcohol to the diolefin dimer to give the ester of an alkadienoic acid.

Description of the prior art The reaction of butadiene with methanol, ethanol, isopropanol, etc., in the presence of his (triphenylphosphine) palladium maleic anhydride and other palladium catalysts such as palladium chloride to form unsaturated ether materials has been reported by S. Takahashi et al., Tetrahedron Letters, No. 26, pages 2451-2453 (1967). Also, Tsuji in Organic Snythesis by Noble Metal Compounds, reports that conjugated dienes when treated with palladium chloride from beta,gamma-unsaturated esters but without a concomitant dimerization of the conjugated diolefins. The prior art also discloses processes for the formation of carboxylic acids and carboxylic acid esters through carbonylation of dienes (see eg US. 3,437,676 and U.S. 3,501,518). Other workers have disclosed processes for making 0,, acids by first making the ester (see US. 2,640,- 074). Finally, a process for forming C esters through olefin carbonylation has been reported (see US. 2,868,813), however, no butadiene dimerization occurs as is true for most of the prior art processes with the result that a monoolefin having n carbons yields a carboxylic acid ester having n+1 carbons.

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SUMMARY OF THE INVENTION Now in accordance with the present invention, it has unexpectedly been discovered that esters of alkadienoic acids can be selectively synthesized through a process which includes the catalyzed dimerization of conjugated aliphatic diolefins followed by the carbonylation and esterification of the resulting dimer the resulting alkadienoic acid ester therefore has 2n plus 1 carbons where n is the carbon number of the conjugated diolefin reagent. The reaction is conducted in a liquid phase using a homogeneous reaction system. The process is normally carried out at temperatures of from about C. to about C. with carbon monoxide pressures ranging from atmospheric to superatmospheric in the substantial absence of oxygen. The catalyst system used to promote the reaction comprises a material that will provide a source of zerovalent palladium at reaction conditions together with a phosphine activator or extraenous amounts of said activator may be added.

The reaction for the formation of the alkadienoic acid esters, it is believed, proceeds in a manner illustrated by the following equation:

Equation 1 demonstrates the reaction of 2 moles of butdiene with a monohydroxy] alcohol such as methanol and gaseous carbon monoxide in the presence of tetrakis (triphenylphosphine) palladium to form the resulting esterified, carboxylated dimer, i.e. methyl trans 3,8-nonadienoate and may be referred to as the methyl ester of nonadienoic acid, a C diene acid. The reaction product is generally composed of greater than about 30 wt. percent of the ester of the corresponding nonadienoic acid prodact.

The starting diolefinic reagent is preferably a C C acyclic, conjugated aliphatic hydrocarbon diolefin including substituted hydrocarbyl moieties. More preferably, however, the aliphatic hydrocarbon diolefins are C -C acyclic conjugated dienes and most preferebly are unsubstituted materials such as butadiene, isoprene, and piperylene. Other non-limiting representative examples of useful starting diolefins includes 2,3-dimethylbutadiene, chloroprene and 2-cyano-1,3-butadiene, 2,3-di-n-butyl-1,3butadiene and the like.

The monohydroxy alcohols to be employed as coreactants have the general formula ROH. The symbols R of the general formula designates a monovalent acyclic or alicyclic organic radical including alkyls having'from 1 to 20, preferably 1 to 12 carbon atoms; and aralkyls having from 7 to 12 carbon atoms. Representative non-limiting examples of useful alcohols include methanol, ethanol, npropanol, lauryl alcohol, n-hexadecylalcohol, isopropylalcohol, secondary butylalcohol, neopentylalcohol, cyclohexanol, benzylalcohol, phenylethylalcohol.

Pure carbon monoxide may be used but it is also possible to employ either commercial gas containing, in addition to carbon monoxide, various constituents such as saturated hydrocarbon or nitrogen, or mixtures of hydrogen and carbon monoxide, i.e. synthesis gas. Carbon monoxide pressures may vary from atmospheric to up to as high as 4,000 p.s.i. The preferred range is from 1,000

3 to 3,000 p.s.i. and the most preferred is from 1500 to 2500 p.s.i. pressure of carbon monoxide.

The reaction for the formation of the alkadienoic acid esters can be carried out in the absence of a solvent or in the presence of an organic diluent that is a substantially inert solvent. It is preferred that the reaction be conducted in a homogeneous reaction system. In most instances the desired homogeneous system can be obtained without the use of solvent systems since the diolefins are usually readily soluble in the monohydroxy alcohol coreactant to which is added the gaseous carbon monoxide. While solvents are not mandatory, representative examples of useful solvent materials include C to C aliphatic ethers and C to C aliphatic and aromatic hydrocarbons, such as pentane, hexane, benzene, toluene, xylene, ethylbenzene, tetrahydrofuran, dimethoxymethane and dioxane.

The catalyst system used to promote the formation of the alkadienoic acid esters is composed of a zerovalent palladium material. This is a zerovalent palladium material or a compound or complex that will yield zerovalent palladium under reaction conditions such as bis- (pi-allyl) palladium. Palladium chloride or complexes of divalent palladium with a suitable reductant such as sodium borohydride or hydrazine will also suflice. Other examples of zerovalent palladium materials are compounds or complexes represented by the general formula L Pd wherein L is a phosphine ligand of the type R R R P and in which the R groups are each independently selected from the group consisting of monovalent acyclic or alicyclic alkyl radicals having from 1 to 20, preferably 1 to 8, carbon atoms; phenyl radicals; monovalent alkylaryl radicals having from 7 to 12, preferably 7 to 10, carbon atoms; and monovalent aralkyl radicals having from 7 to 12, preferably 7 to 10, carbon atoms. Representative examples of useful ligand materials include triphenylphosphine, tribenzylphosphine, tributylphosphine, trioctylphosphine, diethylphenylphoshine, diphenylcyclohexylphosphine, diphenyldodecylphosphine, diphenyl-s-butylphosphine, etc. Palladium materials that will generate the desired zerovalent palladium under reaction conditions include materials such as tetrakis(triphenylphosphine)pa1- ladium, tetrakis(tribenzylphosphine)palladium, tetrakis- (trioctylphosphine)palladium, bis(pi-allyl)palladium and palladium acetate, palladium chloride or complexes of divalent palladium with sodium borohydride, hydrazine or other suitable reductants. These catalysts are sensitive to oxygen and mineral acids; hence maximum catalyst efliciency is secured by purification of the reactants prior to use. Oxygen removal can be secured by purging the reaction system with nitrogen or other inert gases. The substantial absence of mineral acids can be insured by the extraneous addition of a base.

Organic phosphine compounds are to be employed in conjunction with the zerovalent palladium catalyst as catalyst activators. They may be already contained as part of the zerovalent palladium material, or they may be added extraneously to said material. Useful materials can be represented by the general formula R R R P wherein R R and R are monovalent organic radicals having from 1 to 20, preferably 1 to 8, carbon atoms. Most preferably R R and R are monovalent acyclic or alicyclic alkyl radicals having from 1 to 8, preferably 1 to 6, carbon atoms; phenyl radicals, monovalent alkylaryl radicals having from 7 to 12, preferably from 7 to 10, carbon atoms; and monovalent aralkyl radicals having from 7 to 12, preferably 7 to 10, carbon atoms. Examples of useful activator materials include triphenylphosphine, tribenzylphosphine, tributylphosphine, trioctylphosphine, diethylphenylphosphine, tricyclohexylphosphine, diphenylcyclohexylphosphine, diphenyldodecylphosphine, diphenyl-s-butylphosphine, etc. These catalyst activators may be part of the catalyst, for example the use of tetrakis(triphenylphosphine)palladium in the reaction generates in situ, the zerovalent palladium material together with the catalyst activator triphenylphosphine. These catalyst activators may also be added extraneously where they are not part of the initial catalyst material or even where part of the original catalyst material since their addition in some instances tends to increase reactivity and selectivity to the final product.

The reaction for the formation of the alkadienoic acid esters is carried out under reaction conditions which include contacting the reactants in the liquid phase and at temperatures which range from about C.-60 C., more preferably C.l50 C., and most preferred from C. C. The reaction pressure, as was noted before, may range from atmospheric up to 4,000 p.s.i. of carbon monoxide pressure, the most preferred range being from 1,500-2,500 p.s.i. The length of time that the reaction takes depends upon a number of process variables, and it would be well within the common knowledge of one skilled in the art to monitor the rate of the reaction by such techniques as gas chromatography to determine the percentage of product formed. Typically, substantial yields containing upwards of 80% of the ester, are secured within ten to twenty hours for reactions conducted at temperatures between 100 C. and 140 C.

In a typical reaction procedure, the catalyst and diolefin are dissolved in an alcohol solutionfor example, butadiene together with the palladium catalyst and activator is dissolved in a methanol solution to which is added gaseous carbon monoxide at varying pressures. The reactor is heated by means of a heating bath or element up to the temperatures between 100 C. and 140 C. and the catalyst comprised of zerovalent palladium material causes the selective dimerization of the butadiene and allows both the carbon monoxide and methanol to add to the resulting dimer to yield the methyl trans 3,8-nonadienoate as the predominant product.

The novel products produced by the present process have many uses. For example, the product of the butadiene carbonylation dimerization reaction yields a product which may be hydrogenated using conventional means to give methyl pelargonate-a compound useful in making pelargonic acid for the synthesis of brake fluid, surfactants, etc.; also it may be further hydrolyzed to the form nonanol which is useful for the synthesis of plasticizers, cosmetic oils, etc.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is further illustrated by reference to the following non-limiting examples:

Example 1 Into a stainless steel pressure bomb equipped with a glass liner is placed 0.8503 g. tetrakis(triphenylphosphine)-palladium, 320 ml. CH OH and 110.5 g. butadiene, under nitrogen. The bomb is pressurized to 2,000 p.s.i.g. with carbon monoxide then heated at 100 C. for 20 hours. At the end of that time, the reactor is cooled and vented and the contents are poured into 300 ml. of water and extracted with 100 ml. pentane. The pentane layer is separated, dried over MgSO and the pentane then stripped off. There is obtained 3.05 g. product containing 63.3% methyl trans 3,8-nonadienoate as determined by carbon-hydrogen analysis together with NMR and IR and GO. These determinations are as follows:

(1) Carbon-hydrogen analysis.--Found (percent): C, 72.15; H, 9.78. Calculated (percent): C, 71.39; H, 9.59.

(2) NMR: 60 cm. in CDCl II CHz=CH-(CH2)3CH=CHCH1COCH3 Ha Hd Ha. He Hb No. of H's 5 (p.p.m. from TMS) 5.5 (center of complex multiplet). 3.6 (singlet).

3.0 (multiplet).

1.8 (center of complex multlplet) Assignment (2) LR. analysis:

Assignment 7 (cmr (LI=C H2 905. 990

H 965 31 (Trans) Following the general procedure of Example 1, a series of reactions were run in which various catalyst activators, L, were added to tetrakis(triphenylphosphine)palladium. The results are summarized in Table I and show that the addition of various catalyst activators can reduce the overall time required for reaction while increasing yields of the nonadienoate ester in the product. Compare for the zerovalent palladium material and catalyst activator.

which are generated in situ during the course of the reaction; e.g. compare Runs 1 and 3. The addition of smaller amounts can however increase the yield of desired product; e.g. compare Runs 1 and 2.

TABLE 11 002011.

Time Product (hours) (g.) Percent Example 4 Following the general procedure of Example 1, a series of reactions were run at various temperatures using tetrakis (triphenylphosphine) palladium as the catalyst and tri-n-butylphosphine as an additional catalyst activator. The results are summarized in Table III and show the effect that temperature has on the overall yield of ester product. Comparison of Runs 1, 2 and 3 as found in this table show that as the temperature is increased above C. the yields of ester product decrease.

TABLE III -o 0,011.

Run (Ph PhPd (II-C4HP)BP T., Time Product N o. (g.) (g.) 0. (hours) (g.) Percent Example 5 Following the general procedure of Example 1, a series example Run 1 with Runs 4-6, 10, 12, 13, etc. 35 of reactions were run at various CO pressures using TABLE I L Time Product Run number (Ph;P)4Pd(g.) L (g.) (hours) Percent 0. 8503 20 3. 05 03. a 0.8208 PhaP 0.9320 15 2.85 42.7 0.8208 Ph P 2.82 15 2.25 5.1 0.8188 (H-C4H9)!P 0.500 15 7.00 78.0 0.8204 504E108? 1.4258 15 10.85 71.2 0.8270 rt-0.118).? 2.1732 15 7.45 04.4 0.8237 (11-C4H0)3P 2.9830 15 4.15 52.1 0.8236 (Il-C4Hn)8P 4.3033 15 2.85 24.5 0.8274 (I1-C4HO)3P 7.2589 15 1.74 2.0 0.8279 map-0H. 0.7100 15 7.55 04.9 0.8174 PIMP-0H. 1.4349 15 3.24 40.4 0.8208 rim-(c2121.). 0 3599 15 8.85 74.0 0.8200 PhP(C2H5)2 05907 15 10.50 70.3 0.8157 PhP(CzH5)8 1 1410 15 5.50 03.0 0.8225 PhP(OzH5)a 1 1840 15 5.20 07.0 0.8261 PhP 0.H.)= 1.7777 15 0.00 38.3

0.8242 Same 1.9914 15 2.05 50.0 0.8250 (CQHEOMP 0.5904 15 1.95 19.31 0.8292 (C;H5O);P 1.1971 15 1.50 1.70

Exam le 3 Following the general procedure of Example 1, a series of reactions were run in which the catalyst was tetrakis (tri-n-butylphosphine) palladium to which additional catalyst activator (n-C I-I P was added. The results are found in Table II and show that in some instances the addition of substantial, extraneous amounts of activator is not essential where the catalyst is comprised of both tetrakis (triphenylphosphine)palladium as the catalyst and tri-n-butylphosphine as an additional catalyst activator. These results can be found in Table IV and show the effect of operating the process at various carbon monoxide pressures. Comparing Runs 1, 2 and 3, it can be seen that the optimum carbon monoxide pressure is 2,000 p.s.1.

7 Example 6 Following the general procedure of Example 1, a series of reactions were run in which 50 vol. percent of the methanol was replaced with another solvent. The catalyst monovalent aralkyl radicals having from 7 to 12 carbon atoms.

4. The process of claim 3 wherein said phosphine activator is an organic phosphine compound having the general formula R R R P where R R and R are monowas tetrakis(triphenylphosphine) palladium and tri-n-bu- 5 l t 1 1 d f h tylphosphine was added as an additional catalyst activator. 3 i i 5 Se ecte Iom t 6 g up conslrlstmg The results of these runs are found summarized in Table f g i 1 to i i p enyl V and show the preferred reaction system for the process ma am y and a y aryl m S avmg 0m 7 to to be a homogeneous one with one of the coreactants, in atoms f 1 4 h l I this case methanol, acting as solvent for the process. 10 e g o fi wherem 3 pa- Compare Run 1 with Runs 2 and 3. mm ca a yst materla as t e genera ormu a.

TABLE V N c 01cm Run (P11 P)1Pd ((n-C H P Added '1., Time Product number (g.) (g.) solvent 0. (hours) (g.) Percent 0.8362 1.4728 THF 120 15 11.41 8.5

Example 7 L Pd Following the general procedure of Example 1, a series of reactions were run in which the efiect of a halogen i.e., gherem L IS a hgand of the type R1R2R3P m 2 and R are selected from the group consisting of 1od1ne, were investigated. The catalyst was tetrak1s(tr1- monovalent alk yl radicals having from 1 to 20 carbon phenylphosph1ne)pallad1um with add1t1onal tri-n-butylatoms, phenyl radicals, monovalent alkylaryl radicals havphosphme added. The results of these reactions are sumin from 7 to 12 carbon atoms and mono 1 nt 1k 1 marized in Table VI and illustrate that addition of halorafiicals having from 7 to 12 carbon atoms Va e am y ii es t pffdl lzgi has htfle efifict on the overall yleld 6. The process of claim 1 wherein said contacting is TABLEVI oment;

Run number ig? (H (g?) 6: 613i??? g Percent E m l 8 conducted with carbon monoxide pressures varying between about 1,000 p.s.i. and 4,000 p.s.i.

Following the general Procedure of Example 1, 117-3 7. The process of claim 6 wherein said diolefin is sebutadiene and 320 methanol e r a d at lected from the group consisting of butadiene, isoprene C. for 15 hours with 2,000 p.s.i. of a 1:1 carbon mond i 1 OXide; hydrogen gas mixture and 0-8330 gof a tfitrflkis 8. A process for the production of esters of nonadiencic (tri-n-octylphosphine)palladium catalyst. There was obacid which comprises contacting butadiene with monotained 7.90 g. product containing 73.7% of methyl transhydroxy alkanols having from 1 to 12 carbon atoms and 3,8-nonadienoate. This example shows high yields of ester carbon monoxide in the presence of a zerovalent pallaproduct are obtainable when synthesis gas is employed dium catalyst material seleected from the group consistas the carbon monoxide reactant. ing of tetrakis(triphenylphosphine)palladium, tetrakis- What is claimed is: (tribenzylphosphine)palladium and tetrakis(trioctylphos- 1. A process for the production of alkadienoic acid phine)palladium and an organic phosphine activator at esters which comprises contacting a C to C acyclic contemperatures of from about 90 to about 150 C. for a jugated aliphatic diolefin with a C to C monohydroxy time sufiicient to recover a yield of the corresponding alcohol and a source of gaseous carbon monoxide in nonadienoate. the presence of a zerovalent palladium catalyst material 9. The process of claim 8 wherein said zerovalent palselected from the group consisting of tetrakis(triphenylladium material is tetrakis(triphenylphosphine)palladium phosphine) palladium, tetrakis(tribenzylphosphine) paland said organic phosphine activator is selected from the ladium and tetrakis(trioctylphosphine) palladium and a g p consisting of p y p p ylphosphosphine activator at reaction conditions and recovering P ylp p in ctylphosphine, diethylphenylthe corresponding alkyl alkadienoate having 2n plus 1 p phine, p y y p p tricyclohexylphoscarbon atom where n is the carbon number of said di- Phine and y p p ineolefin. 10. The process of claim 8 wherein said monohydroxy 2. The process of claim 1 wherein said contacting is al a Ol is methanol and the contacting is carried out at carried out at a temperature ranging from about 80 to carbon monoxide pressures of from about 1,500 p.s.i. to about 160 C. about 2,500 p.s.i.

3. The process of claim 2 wherein said monohydroxy 11. The process of claim 1 wherein said zerovalent palalcohol has the general formula ROH, where R is a monoladium catalyst material is tetrakis(triphenylphosphine) valent organic radical selected from the group consisting palladium and said phosphine activator is tributylphosof alkyl radicals having from 1 to 20 carbon atoms, and phine.

9 10 12. The process of claim 8 wherein said zerovalent OTHER REFERENCES Palladium cfatalyst material tetrakisgtriphepylpho? Chemical Abstracts, vol. 68, 104488k (1968). phinflpauadmfn and said orgamc phosphme actlvator 1s Billups et al.: The Palladium-Catalyzed Carbonylation tnbutylphosphme' Dimerization of Butadiene, J. Chem. Soc. (D), No. 18,

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